23.3 How to construct the tangent lines from a point to a circle with a rule and a compass. 145 23.3 How to construct the tangent lines from a point to a circle with a rule and a compass. P O \begin{tikzpicture} \tkzPoint(0,0){O} \tkzPoint(9,2){P} \tkzDefMidPoint(O,P) \tkzGetPoint{I} \tkzDrawCircle[R](O,4cm) \tkzDrawCircle[diameter](O,P) \tkzCalcLength(I,P) \tkzGetLength{dIP} \tkzInterCC[R](O,4cm)(I,\dIP pt)\tkzGetPoints{Q1}{Q2} \tkzDrawPoint[color=red](Q1) \tkzDrawPoint[color=red](Q2) \tkzDrawLine(P,Q1) \tkzDrawLine(P,Q2) \tkzDrawSegments(O,Q1 O,Q2) \tkzDrawLine(P,O) \end{tikzpicture} tkz-euclide AlterMundus